A conventional hearing aid comprises a main body case, a battery case provided so that it can be pulled from inside the main body case to outside of the main body case, a control device that is actuated by electromotive force of an air battery housed in the battery case, a microphone and speaker electrically connected to the control device, and a switching portion for cutting off power from the air battery to the control device when the battery case is pulled out of the main body case.
When a hearing aid such as this is in its storage state, that is, when it has been removed from the ear at bedtime, for example, the design is such that when the battery case is pulled out of the main body case after the hearing aid is removed from the ear, a switching portion cuts off the power from the air battery to the control device.
Even when the switching portion cuts off the power from the air battery to the control device here, the air holes in the air battery are still open, and the chemical reaction with oxygen continues, so the battery capacity gradually decreases.
Patent Literature 1, for example, discloses a technique for extending the life of an air battery by using a cover to open and close the air holes of the air battery, and opening and closing the switching portion with a manipulation component provided to the outer face of the main body case.